Liquid crystal display apparatus and optical device for use therein

ABSTRACT

For obtaining both high brightness under condition of small size and simplified structure, and for achieving suppression of increase in temperature of liquid crystal display elements and polarizing elements in a liquid crystal display apparatus, a liquid crystal display element converts light from a light source into a display picture depending on a driving signal, and an optical projection system contains a first optical element and projects a light signal toward an object of projection. A space is defined by an incident side polarizing element or the liquid crystal display element, the first optical element and a holding member, and the space is filled up with a cooling medium.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display apparatus forprojecting a picture on a screen with use of a liquid crystal displayelement, such as a liquid crystal projector, a liquid crystaltelevision, a projection type display device, and so on, and alsorelates to an optical device for use therein.

2. Description of Related Art

Conventionally, in a display apparatus for projecting a picture on ascreen with use of a liquid crystal display element, upon the liquidcrystal display element of such as a liquid crystal panel or the like, alight is irradiated from a light source, such as a light bulb, etc., andthe light penetrating or transmitting through it is projected on thescreen. By adjusting or regulating an amount or quantity of polarizationat each pixel in the liquid crystal element, the display is performed oraccomplished.

In such a liquid crystal display apparatus, upon a requirement from auser of obtaining a good projection picture even in a brightcircumstance or place, conventionally, an attempt was made to increasethe optical output of the projected picture by enhancement in abrightness of the light source and/or by improvement in the utilityefficiency of the light beam thereof. For instance, with a technologydescribed in Japanese Patent Laid-Open No. Sho 63-197913 (1988), thereare utilized a polarization conversion element which comprises apolarized light separation means for dividing or separating an irregularpolarized light from the light source into two (2) polarized lights thatare orthogonal to each other, and a polarization direction rotatingmeans for rotating one of the polarized lights separated into adirection consistent with that of the other polarized light, therebyimproving or increasing the utility efficiency of the light.

In the liquid crystal display apparatus as mentioned in the above,within the light emitted from the light source, the light except thatbeing projected finally is absorbed into the liquid crystal displayelement and optical elements and so on, in the periphery thereof, andgenerates heat. Therefore, the liquid crystal display element and theoptical elements and so on in the periphery thereof are heatedtherewith. In particular, the increase in the output of the projectionlight, for purpose of increasing the brightness of the light sourceand/or of improving the utility efficiency of the light, results in theincrease in light amount being incident upon the liquid crystal displayelement, and also leads to the increase in the heat generation of theliquid crystal display element and polarizing plates. Further, in a casewhere such a polarization conversion element is used within an opticalsystem reaching from the light source until the polarizing element at anincidence side, because the polarized lights are aligned equally in thepolarization direction thereof, the amount of heat generation becomeslarge in the polarizing element at a light exit side when black isdisplayed totally all over the display.

On the other hand, the liquid crystal display element is, in general,constructed with a semiconductor driving element and optical functionparts or elements, such as liquid crystals, and so on. For keepingliquid crystals functioning normally, they must be kept at a temperaturelower than a predetermined value (less than 60° C., for example).Therefore, cooling is necessary for the liquid crystal display element.As a cooling method for this kind, there have been made many proposals.

As a conventional art relating to the cooling of the liquid crystaldisplay element, for instance, an example which is described in JapanesePatent Laid-Open No. Hei 3-174134 (1991) is already known. In thisconventional art, one of a pair of polarizing plates and the liquidcrystal panel as the liquid crystal display element are disposed, beingclosely contacted with a cooler which contains a cooling liquidhermetically therein. The cooler is hermetically constructed with aframe and two (2) pieces of transparent plates which close or cover onboth side surfaces of the frame, and the polarizing plate mentionedabove and the liquid crystal panel are closely contacted with thetransparent plate, respectively. A part of a heat pipe is inserted intothe cooler, and another portion protruding outside the cooler isprovided with radiator fins. The heat in the liquid crystal panel andthe polarizing panel is transferred to the cooler, further passingthrough the cooling liquid and the heat pipe, and then it is radiatedfrom the radiator fins to the outside of the cooler.

Further, in the display apparatus described in the above, a part of thelight passing through the liquid crystal display element sometimes mayhappen to be reflected by the optical element, such as a projectionlens, behind the liquid crystal element, thereby coming back to theliquid crystal display element. Such reflection light comes to be acause of lowering in quality of the projection picture, in particular,such as a decrease in contrast thereof.

As a conventional technology for suppressing the decrease in thecontrast due to the reflection light from the optical element behind theliquid crystal display element, other than a measure of improving thetransparency (or transmission coefficient) by coating the opticalelement, there is known another technology which is described inJapanese Patent Laid-open No. Hei 6-110055, for example. With thisconventional technology, a so-called λ/4 plate is positioned between thepolarizing plate at the light exit side and the projection lens. Thelight penetrating through the liquid crystal panel and the polarizingplate at the light exit side reaches through the λ/4 plate to theprojection lens. A portion of this incident light is reflected by theprojection lens and comes back in the direction of the liquid crystalpanel. At this moment, the reflected light has passed through the λ/4plate two (2) times after passing through the polarizing plate at thelight exit side. Therefore, it is rotated by 90 degrees in thepolarization direction thereof, comparing to passing through the λ/4plate previously. Therefore, the reflection light is unable to passthrough the polarizing plate at the light exit side, thereby beingabsorbed totally therein.

With the conventional technology for protecting the liquid crystaldisplay element from the heating, since one of the polarizing plates andthe liquid crystal display element are positioned so that they areclosely contacted with the transparent plates of the cooler whichcontains the cooling liquid hermetically therein, there are two (2)pieces of the transparent plates and the cooling liquid between thepolarizing plate and the liquid crystal display element. And, sincethere occurs reflection due to a change in the refractive index on eachboundary surface, the penetration light is easily attenuated therewith.

Further, with this conventional technology, since it is constructed insuch a manner that the heat generation from the liquid crystal displayelement is radiated through a large number of heat transmission routes,i.e., the transparent plate cooling liquid heat pipe radiator finsperipheral atmosphere (outside air), it is easily affected in thecooling efficiency thereof by an integration or summation of thermalresistance, and is complex in the structure thereof. In particular, forachieving high brightness, there is a necessity of increasing theefficiency in heat radiation; therefore, a large heat pipe and/or largeradiator fins are needed.

While, in the above-mentioned conventional technology for suppressingthe decrease in the contrast, since it has such a construction that thereflection light from the projection lens is absorbed with thepolarizing plate at the light exit side, that polarizing plate at thelight exit side is heated up more easily. This heating-up is a cause ofthermal deterioration (including deformation) of the polarizing plate atthe light exit side. Further, additional provision of the λ/4 platebrings an increase in the number of the optical parts and complexity inthe structure thereof.

SUMMARY OF THE INVENTION

An object of the present invention is, therefore, to provide a liquidcrystal display apparatus and an optical device for use therein,achieving a high brightness of picture with a small-sized and simplifiedstructure, as well as suppression of increase in temperature of theliquid crystal display element and the polarizing elements therein.

For achieving the above-mentioned object, in accordance with the presentinvention, there is provided a liquid crystal display apparatus,comprising:

an optical source system for emitting projection light;

a liquid crystal display portion, for receiving the emission light fromsaid optical source of the optical system and for generating a pictureto be projected depending upon a given driver signal;.

an optical projection system, including a first optical element whichreceives a light emitted from said liquid crystal display portion, andfor projecting the light emitted from said liquid crystal displayportion towards a projection object, wherein said liquid crystal displayportion comprises:

a liquid crystal display element for generating the picture;

an incident side polarizing element being positioned at an incident sideof said liquid crystal display element;

an exit side polarizing element being positioned at an exit side of saidliquid crystal display element;

a holding member for holding at least the liquid crystal displayelement, the exit side polarizing element and said first opticalelement; and

a cooling medium, wherein either one of said incident side polarizingelement or said liquid crystal display element, said first opticalelement and said holding member define a space between said liquidcrystal display element and said first optical element, and said coolingmedium is filled up within said space.

Further, in accordance with the present invention, there is provided aliquid crystal display apparatus, comprising:

an optical source system for emitting projection light;

a plurality of liquid crystal display portions, for receiving theemission light from said optical source of the optical system and forgenerating a picture to be projected depending upon a given driversignal;

an optical projection system for composing and for projecting the lightemitted from said plurality of liquid crystal display portions towards aprojection object, wherein:

said optical source system has a light source and an optical separationsystem for dividing and emitting the light emitted from the light sourcetowards said plurality of liquid crystal display portions; and

said optical projection system has a first optical element for composinglights emitted from said plurality of liquid crystal display portionsand a second optical element for projecting the light composed, andfurther, each of said liquid crystal display portions comprises:

a liquid crystal display element for generating the picture;

an incident side polarizing element being positioned at an incident sideof said liquid crystal display element;

an exit side polarizing element being positioned at an exit side of saidliquid crystal display element;

a holding member for holding at least the liquid crystal displayelement, the exit side polarizing element and said first optical elementin each of said liquid crystal display portions; and

a cooling medium for cooling, wherein either one of said incident sidepolarizing element or said liquid crystal display element, said firstoptical element and said holding member define a space between saidliquid crystal display element and said first optical element, and saidcooling medium is filled up within said space.

In this instance, said holding member is provided for each of saidliquid crystal display portions, and the space within which said coolingmedium is filled up is defined for each of said liquid crystal displayportions.

Alternatively, said holding member is provided in common for said liquidcrystal display portions, and the space within which said cooling mediumis filled up is defined as one space as a whole for said liquid crystaldisplay portions.

Furthermore, in accordance with the present invention, there is provideda liquid crystal display apparatus, comprising:

an optical source system for emitting projection light;

a plurality of liquid crystal display portions, for receiving theemission light from said optical source of the optical system and forgenerating a picture to be projected depending upon a given driversignal;

a projection optical system for composing and for projecting the lightemitted from said plurality of liquid crystal display portions towards aprojection object, wherein:

said optical source system has a light source and an optical separationsystem for dividing and emitting the light emitted from the light sourcetowards said plurality of liquid crystal display portions; and

said optical projection system has a first optical element for composinglights emitted from said plurality of liquid crystal display portionsand a second optical element for projecting the light composed, andfurther, each of said liquid crystal display portions comprises:

a liquid crystal display element for generating the picture;

an incident side polarizing element being positioned at an incident sideof said liquid crystal display element;

an exit side polarizing element being positioned at an exit side of saidliquid crystal display element;

a holding member for holding at least the liquid crystal displayelement, the exit side polarizing element and said second opticalelement; and

a cooling medium for cooling, wherein said holding member is provided incommon for said liquid crystal display portions, as well as, in each ofsaid liquid crystal display portions, either one of said incident sidepolarizing element or said liquid crystal display element, said secondoptical element and said holding member define a space between saidliquid crystal display element and said second optical element, thespace within which said cooling medium is filled up is constructed asone space as a whole for the liquid crystal display portions, and saidcooling medium is filled up within said space.

Here, said first optical element can be so constructed that it isreceived within said space.

Moreover, in accordance with the present invention, there is provided anoptical device; including a liquid crystal display element within anoptical path, comprising:

an incident side polarizing element positioned at an incident side ofsaid liquid crystal display element;

an exit side polarizing element positioned at an exit side of saidliquid crystal display element;

fixing means for fixing said incident side polarizing element, saidliquid crystal display element and said exit side polarizing element;

a cooling medium; and

holding means for holding said cooling medium under a condition ofcontacting with said exit side polarizing element.

In each invention in the above, according to the present invention,further, the following embodiments can be applied as appropriate:

a) said exit side polarizing element is positioned at an incidentsurface of said first optical element.

b) said exit side polarizing element is fixed on a surface at an exitside of said liquid display element.

c) said exit side polarizing element is located between said liquidcrystal display element and said first optical element and positionedunder condition of being apart from both of them.

d) said holding member has openings at the incident side and the exitside, respectively, and further, at said incident side opening isinstalled any one of said incident side polarizing element and saidliquid crystal display element, and at said exit side opening isinstalled said first optical element.

e) at the incident side opening of said holding member is installed saidincident side polarizing element, and said liquid crystal displayapparatus is held by said holding member under condition that thecooling medium lies on both surfaces at the incident side and the exitside thereof.

f) at the incident side opening of said holding member is installed saidliquid crystal display element, and said liquid crystal displayapparatus is held by said holding member under condition that thecooling medium lies on a surface of the incident side thereof.

g) said liquid crystal display portion is held by said holding memberunder condition that at least said exit side polarizing element contactswith said cooling medium.

h) said cooling medium has a refractive index near to that of said exitside polarizing element.

i) the refractive index of said cooling medium lies within a range from1.2 to 1.7.

j) said holding member is made of metal and provided with a heatradiation fin.

k) said holding member is made of metal and provided with a pressureadjusting mechanism.

l) said optical source system comprises an optical source and an elementfor converting the light projected from the light source in thepolarization thereof, so that the incident light upon said incident sidepolarizing element comes to be a polarized light including apolarization component being in parallel to a polarization direction ofsaid incident side polarizing element.

With such a liquid crystal display apparatus, it is possible to suppressthe increase in temperature of the liquid crystal display element andthe polarizing element(s), and also to suppress the change in therefractive index in the optical path at the exit side of the liquidcrystal display element to a low level.

By suppressing the change in the refractive index, the light reflectedback to the liquid crystal display means is reduced. As a result, highbrightness of the picture is accomplished. Further, since there is nonecessity of a special optical parts or element such as the λ/4 plate,and since the structure for the cooling can be simplified with ease andhas high efficiency, the apparatus can be small-sized and simplified inthe construction as a whole.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-section view showing structural elements of a liquidcrystal display portion in accordance with a first embodiment of thepresent invention;

FIG. 2 is a cross-section view showing structural elements of a liquidcrystal display element for use in the present invention;

FIG. 3 is a view showing an optical system of a single-plate type liquidcrystal projector as a whole, relating to the first embodiment of thepresent invention;

FIG. 4 is a cross-section view showing structural elements of a liquidcrystal display portion in accordance with a second embodiment of thepresent invention;

FIG. 5 is a cross-section view showing structural elements of a liquidcrystal display portion in accordance with a third embodiment of thepresent invention;

FIG. 6 is a cross-section view showing structural elements of a liquidcrystal display portion in accordance with a fourth embodiment of thepresent invention;

FIG. 7 is a cross-section view showing structural elements of a liquidcrystal display portion in accordance with a fifth embodiment of thepresent invention;

FIG. 8 is a view showing structure at the periphery of the liquidcrystal display portion in the fifth embodiment of the presentinvention;

FIG. 9 is a view showing an optical system of a three(3)-plate typeliquid crystal projector as a whole, relating to the fifth embodiment ofthe present invention;

FIG. 10 is a cross-section view showing structural elements of a liquidcrystal display portion in accordance with a sixth embodiment of thepresent invention;

FIG. 11 is a cross-section view showing structural elements of a liquidcrystal display portion in accordance with a seventh embodiment of thepresent invention;

FIG. 12 is a view showing structure at the periphery of the liquidcrystal display portion in the eighth embodiment of the presentinvention;

FIG. 13 is a view showing structure at the periphery of a syntheticoptical element in the ninth embodiment of the present invention;

FIG. 14 is a cross-section view showing structural elements of a liquidcrystal display portion in accordance with a tenth embodiment of thepresent invention; and

FIG. 15 is a cross-section view showing structural elements at theperiphery of the liquid crystal display portion in the eleventhembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of a liquid crystal projector according to thepresent invention will be fully explained by referring to the attacheddrawings.

As an embodiment, described here is a case of a liquid crystalprojector.

First to third embodiments of the present invention will be explained byreferring to attached FIGS. 1 through 6.

FIG. 3 shows an example of structure of an optical system of asingle-plate type liquid crystal projector. This single-plate typeliquid crystal projector is constructed to have a light source 12 suchas a metal halide lamp, etc., a reflection mirror 13 for condensing thelight emitted from the light source 12 into a constant direction,multiple lenses 14 and 15 assembling a large number of cell lenses, apolarization conversion element 17 for aligning the polarized light intoa direction, a liquid crystal display portion 11 and a group ofprojection lenses 1 b.

A picture displayed on the liquid crystal display portion 11 isprojected through the projection lenses 1 b upon a screen 16, whereby anenlarged picture is displayed on the screen.

Here, components from the light source 12 to the polarization conversionelement 17 constitute an optical source system for generating aprojection light to be incident upon the liquid crystal display portion11. Further, from a viewpoint of structure, an optical projection systemis formed with a first lens 1 a and the projection lens group 1 b whichare included in the liquid crystal display portion 11.

The polarization conversion element 17 is able to convert an incidentirregular polarization light into a polarized light of a particularpolarization component with good efficiency. In the present embodiment,this polarization conversion element 17 is so constructed and positionedthat a polarized light can be obtained which is almost in parallel tothe polarization direction of an incident side polarizing element 3 a.

FIG. 1 is a cross-sect ion view showing structural elements of a liquidcrystal display portion in accordance with a first embodiment of thepresent invention. The liquid crystal display portion 11 comprises aliquid crystal display element 2, an exit side polarizing element 3 b, afirst projection lens 1 a, a holding member 6 for holding thesecomponents and a cooling medium 5, and an incident side polarizingelement 3 a. Also, a reference numeral 90 indicates a progressiondirection of the light.

The first projection lens 1 a is an optical element which is part of theprojection lens group with the above-mentioned projection lens group 1b, and is positioned at a side of the projection lens group nearest tothe liquid crystal display element 2. The incident side polarizingelement 3 a, the liquid crystal display element 2, the exit sidepolarizing element 3 b and the first projection lens 1 a are sopositioned that their respective light permeating surfaces are almost inparallel to one another.

The holding member 6, in the present embodiment, has a function ofholding the liquid crystal display element 2 and the exit sidepolarizing element 3 b so as to contact with the cooling medium 5 forcooling thereof. Because of this, that member, with other members, alsofunctions as a member for defining a cooling space within which thecooling medium 5 lies, i.e., a member acting as a container for thecooling medium 5. For those other members, in the present embodiment,the liquid crystal display element 2, the first projection lens 1 a, abellows 9 for pressure adjusting and so on function as the membersdefining the cooling space enclosing the cooling medium therein. Thepressure adjusting bellows 9 absorbs a change in volume of the coolingmedium 5. Further, with the holding member 6 is connected a heatradiation fin 19, thereby heat-exchanging the heat of the cooling medium5 between an external fluid, such as air, to cool down the coolingmedium 5.

The holding member 6 has a first holding portion 61 of a concavity shapeand a second holding portion 62 of a plate-like shape. At an opening ofthe concave of the first holding portion 61, the second holding portion62 is connected through an O-ring 7 a. Further, in the second holdingportion 62 is formed an incident side opening 62 a which is sealed withthe liquid crystal display element 2. Further, in the first holdingportion 61, there are formed an exit side opening 61 a which is sealedwith the first projection lens 1 a and an opening 61 b which is sealedwith the pressure adjusting bellows 9. Both the incident side opening 62a and the exit side opening 61 a have such sizes that they will notinterrupt the incident light and exit light into/from the liquid crystaldisplay element 2 therewith.

In the incident side opening 62 a is inserted the liquid crystal displayelement 2, with press-fitting an elastic body 20 in an aperturetherebetween. In the exit side opening 61 a is inserted the firstprojection lens 1 a, which is press-contacted through the O-ring 7 b.

The incident side polarizing element 3 a is positioned with keeping aconstant distance between the liquid crystal display element 2, and issupported by an incident side polarizing element holding frame 4 a. Onthe other hand, the exit side polarizing element 3 b is positioned on anincident surface of the first projection lens 1 a, and is supported byan exit side polarizing element holding frame 4 b. Here, both theincident side polarizing element holding frame 4 a and the exit sidepolarization element holding frame 4 b have such shapes that they willnot interrupt the incident light upon the liquid crystal display element2.

The pressure adjusting bellows 9 is attached at the opening of theholding member 6 through a pressure adjusting bellows pressing plate 10.The space which is surrounded by the liquid crystal display element 2,the holding member 6, the first projection lens 1 a and the pressureadjusting bellows 9, is in a condition of being sealed liquid-tight, toretain the cooling medium 5.

Each of the elements mentioned above will be explained in more detailbelow.

FIG. 2 shows a cross-section of the liquid crystal display element 2. Asis shown in the figure, the liquid crystal display element 2 isconstructed with a liquid crystal driven display portion 50, glassplates 51 and 52, and a liquid crystal display element frame 53. To theliquid crystal display element 2 is electrically connected a signal line18 for driving the liquid crystal display element. This liquid crystaldisplay element driving signal line 18 is fixed to the liquid crystaldisplay element 2 with adhesive 54, and is used to transmit a drivingsignal outputted from a driver circuit not shown in the figure.

The incident side polarizing element 3 a and the exit side polarizingelement 3 b are formed in a plate-like shape, and are coated with glassor resin on one side surface thereof, respectively. The incident sidepolarizing element 3 a and the exit side polarizing element 3 b have thefunction of penetrating or transmitting through only a light componentin a desired vibration direction. However, for the incident sidepolarizing element 3 a and the exit side polarizing element 3 b, aplurality of polarizing elements can be applied.

For the cooling medium 5, a transparent fluid is used which has arefractive index that is equal to or more than 1.2 and is equal to orless than 1.7. As the transparent fluid in a range from 1.2 to 1.7 inthe refractive index, for example, there are listed an inactive liquidof fluoride (refractive index 1.25-1.3), ethylene glycol (refractiveindex 1.43), glycerin (refractive index 1.47), and aqueous solution andglycerin.ethylene glycol liquid mixture of those, etc.

Preferably, the refractive index of the cooling medium 5 is nearly equalto the refractive index of the optical element which contacts with thecooling medium 5 on an optical path, such as the liquid crystal displayelement 2 and the exit side polarizing element 3 b. Here, the refractiveindex of the optical glass or plastic which is used in the liquidcrystal display element 2, the exit side polarizing element 3 b and thefirst projection lens, and so on, is about 1.4-1.5. Since glycerinethylene glycol liquid mixture is 1.45 in the refractive index thereof,it is preferable as the cooling medium 5. Of course, if satisfying theabove condition, also other materials which are not listed here can beused.

By selecting the cooling medium 5 in such a manner, a difference in therefractive index upon the boundary surface between the liquid crystaldisplay element 2 and the cooling medium 5, and upon the boundarybetween the cooling medium 5 and the exit side polarizing element 3 b,comes to be small. Thereby, the reflection upon those boundary surfaces,and also the decrease in the contrast due to the reflection light comingback into the liquid crystal display element, can be suppressed.

The holding member 6 is made of a metal having superior thermalconductivity, such as, Fe, Cu, Al, Mg, etc. or materials containing themtherein. In a holding portion 62 which is part of the holding member 6,there is provided an incident side opening of about rectangular shapewhich is larger than a display pixel region of the liquid crystaldisplay element 2. In this opening, the liquid crystal display element 2is inserted, and it is fixed by press fitting of the elastic body 20into an aperture therebetween. In the holding portion 61 is provided anexit opening 61 a of a circular shape which is nearly equal to aneffective diameter of the first projection lens 1 a. In the opening 61 ais inserted the first projection lens 1 a. The first projection lens 1 ais press-fitted and fixed onto a suppressing plate 8 for the firstprojection lens by crushing the O-ring 7 b.

However, in place of the elastic body 20 and the O-ring 7, the liquidcrystal display element 2 and the first projection lens 1 a may be fixedand sealed by use of adhesive, putty, curable resin and so on. Havingsuch structure, it does not happen that the holding member 6 interruptsthe light path of a display light passing through the display pixelregion of the liquid crystal display element 2.

Further, the holding member 6 is formed as a so-called two piecestructure with holding portions 61 and 62, and the connecting portion ofthose come to be in a condition of being sealed liquid-tight by crushingthe O-ring 7 a. In this way, with such a structure of making the holdingmember from a plurality pieces thereof, it is possible to make a volumeof the space in which the cooling medium 5 is sealed large, irrespectiveof the sizes of the incident side opening 62 a and the exit side opening61 a of the holding member 6, and irrespective of an optical distancefrom the liquid crystal display element 2 up to the first projectionlens 1 a. It is also possible to make the holding member a one piecestructure, of course, to simplify the structure of the liquid crystaldisplay portion 11.

On the holding portion 61 is fixed the pressure adjusting bellows 9 withthe pressing plate 10 for the pressure adjusting bellows. With thispressure adjusting bellows 9, the volume change of the cooling medium 5due to change in temperature thereof is absorbed by expansion andshrinkage of the pressure adjusting bellows 9, thereby maintaining thepressure of the cooling medium 5 constant.

The exit side polarizing element 3 b is fixed onto the holding portion61 by the exit side polarizing element holding frame 4 b. This exit sidepolarizing element holding frame 4 b is so shaped that it will notobstruct a convection current of the cooling medium or the optical path.

A part of the heat generated by the liquid crystal display element 2 istransmitted through the elastic body 20 to the holding member 6, and isradiated to an outside of the liquid crystal display portion 11. Most ofthe heat remaining is absorbed into the cooling medium 5 and movesfollowing the natural convection current of the cooling medium 5. Then,it is transferred to an interior wall surface of the holding member 6 tobe radiated outside. Most of the heat generated in the exit sidepolarizing element 3 b is absorbed by the cooling medium 5 and isradiated outside.

In this manner, the holding member 6 has a role of radiating the heatgenerated in the liquid crystal display portion 11 outside. withprovision of the radiation fin 19 on an external wall of the holdingmember 6, the efficiency of the radiation can be increased. In the caseof heat radiation by the natural convection current of the air, it ispreferable that the heat radiation surface of the heat radiator fin 19is disposed almost in parallel with a vertical direction. However,though the heat radiator fin 19 is provided on the holding portion 61 inthe figure, it can be provided on holding portion 62 or on both holdingportions 61 and 62. With compulsive cooling of the holding member 6 bymeans of a cooling fan and so on, the efficiency of the heat radiationcan be increased much more. In this case, it is preferable that the heatradiator fin 19 be so disposed that the heat radiating surface thereofis about in parallel with the direction of the air flow by the coolingfan. Further, in the case where the cooling is performed by the naturalconvection current as in the present embodiment, a low noise cooling canbe achieved without generation of noise from the fan and so on.

A part of the heat generated in the incident side polarizing element 3 ais heat-exchanged into a periphery portion through contact thermalconduction, and a part of the remaining is heat-exchanged between aperipheral atmosphere. compulsive cooling is also applicable by causingan air current upon the surface of the incident side polarizing element3 a with use of the cooling fan.

Furthermore, it is also possible to accelerate or improve the heatradiation to an outside of the liquid crystal display portion 11 throughcontact thermal conduction, by using a structure made of a material ofgood thermal conductivity, such as a metal, Fe, Al and the like, ormaterials containing them therein, for holding and fixing the liquidcrystal display portion 11 as a whole.

In the present embodiment, since at least an incident side portion ofthe liquid crystal display element 2 faces an outside of the holdingmember 6, and an electrical connection between the liquid crystaldisplay element 2 and the signal line 18 for driving the liquid crystaldisplay element is provided in an outside of the holding member 6, theelectrical connection and the liquid crystal display element drivingsignal line 18 are prevented from touching or contacting the coolingmedium 5. Because of this, there is no necessity of a measure forprotecting from encroachment or corrosion by the cooling medium 5.

Further, the exit surface of the liquid crystal display element 2 is notin contact with the peripheral atmosphere (outside air); therefore,without the adhesion of dust in the peripheral atmosphere (outside air)onto the exit surface of the liquid crystal display element 2, no shadowis cast on the projection picture.

The exit side polarizing element 3 b need not necessarily be in onepiece as in the present embodiment, but it can be constructed with aplurality of pieces thereof, and even in a case where a portion of theplurality of pieces is attached onto the liquid crystal display element2, the effect of the present invention is still effective.

In the construction mentioned in the above, as shown in FIG. 3, thelight emitted from the light source 12 is condensed into the multiplelenses 14 and 15 by the reflection mirror 13. Here, the multiple lenses14 and 15 function to permit the entry of the light into the liquidcrystal display element 2 equally over a whole surface of the displaypixel region thereof, thereby enabling an equal brightness on the screen16. The light passing through the multiple lenses 14 and 15, after beingconverted into a polarized light which is almost in parallel to thepolarization direction of the incident side polarizing element 3 throughthe polarization conversion element 17, is incident upon the liquidcrystal display portion 11. Then, the light incident upon the liquidcrystal display portion 11 is adjusted in darkness (i.e., bright ordark) for each of the pixels corresponding to the picture to bedisplayed in the liquid crystal display portion, and is then projected,through the group of the projection lenses constructing the projectionmeans, on the screen 16.

In the polarization conversion element 17, by obtaining the polarizedlight almost in parallel to the polarization direction of the incidentside polarizing element 3, the permeability in the incident sidepolarizing element 3a is increased, and the emitted light of the lightsource 12 reaches to the liquid crystal display element 2 with goodefficiency. Further, in the incident side polarizing element 3 a, sincean amount of the light is absorbed therein, the heat generation becomessmall.

As is explained in the above, according to the present embodiment, thesuppression of a decrease in the contrast of the projection picture canbe achieved. As a result of this, the projection picture of highbrightness can be obtained. Further, the increase in the temperature ofthe liquid crystal display element 2 and the exit side polarizingelement 3 b can be suppressed. Furthermore, since other special opticalelements are not necessitated, simplification of the liquid crystaldisplay portion 11 can be achieved. Moreover, without using a heat pipe,the cooling can be performed with a simple structure.

Next, an explanation will be given of another embodiment of the liquidcrystal display portion 11 which is applied to the single-plate typeliquid crystal projector, by referring to FIGS. 4 through 6. However, inthe drawings used below, the structural elements which have the samefunctions as those in the first embodiment are attached with the samereference numerals. Further, the liquid crystal display portion 11 belowis also applied to the single-plate type liquid crystal projector shownin FIG. 3.

FIG. 4 is a cross-section view showing each element or portion of theliquid crystal display portion according to the second embodiment of thepresent invention.

The present embodiment differs from the first embodiment in an aspectthat the exit side polarizing element 3 b is fixed onto the exit surfaceof the liquid crystal display element 2. This enables a structure inwhich a penetrating axis of the polarized light at the exit sidepolarizing element 3 is positioned in advance, with high accuracyrelating to the liquid crystal display element 2, and then is fixed.Because of this, the permeability or transmittance when displaying whitein total and a shielding ratio when displaying black in total areimproved, thereby obtaining high contrast.

Further, in the present embodiment, when the liquid crystal displayelement 2 is inserted into the opening 62 a, the connecting portion withthe holding portion 61 is sealed by the adhesive 21.

FIG. 5 is a cross-section view showing each element or portion of theliquid crystal display portion according to the third embodiment of thepresent invention.

The present embodiment differs from the first embodiment in aspects thatthe cooling medium 5 is filled up within a region from the exit surfaceof the incident side polarizing element 3 a up to the incident surfaceof the first projection lens 1 a, and that the liquid crystal displayelement 2 is disposed in the cooling medium 5.

In FIG. 5, a reference numeral 24 indicates a liquid crystal displayelement holding frame for positioning and holding the liquid crystaldisplay element 2 in the cooling medium 5, 25 a cooling medium pressureadjusting chamber, and 22 a signal line extending opening provided forextending the liquid crystal display element driving signal line 18outside the holding member.

The incident side polarizing element 3 a is positioned so as to closethe opening 62 a which is formed at the incident side of the holdingportion 62, i.e., an incident opening. Further, the connecting portionbetween the holding member 62 is sealed with an adhesive, putty, O-ringand so on. The cooling medium 5 is filled up within the space surroundedby the incident side polarizing element 3 a, the holding member 6, thepressure adjusting bellows 9 and the first projection lens 1 a.

The liquid crystal display element 2 is supported by the liquid crystaldisplay element holding frame 24 and is disposed in the cooling medium5. Here, the region in which the cooling medium 5 is filled up isconnected with liquid crystal display element 2 at the incident surfaceside and the exit surface side thereof, and the cooling medium 5 canflow between both regions freely with the convection current.

The liquid crystal display element driving signal line 18 is extendedfrom the signal line extending opening 22 to an outside of the holdingmember 6. The signal line extending opening 22 is sealed by filling upwith the adhesive or the curable resin, or by press-fitting of anelastic body. With the seal portion being formed in this manner, theliquid crystal display element driving signal line 18 can be extended orled out to an outside of container.

The cooling medium pressure adjusting chamber 25 provided with thepressure adjusting bellows 9 is communicated with the inside of theholding portion 61 and thereby maintains the pressure of the coolingmedium 5 constant. By dividing the cooling medium pressure adjustingchamber 25 and the holding portion 6 into separate parts, the holdingportions 61 and 62 can be small-sized.

In this manner, according to the present embodiment, since both theincident surface and the exit surface of the liquid crystal displayelement 2 are in contact with the cooling medium 5 directly to becooled, the rise-up of temperature of the liquid crystal display element2 can be reduced much more. Also the heat generation in the incidentside polarizing element 3 a can be cooled down by the cooling medium 5.Further, both surfaces of the liquid crystal display element 2 are outof contact with the peripheral atmosphere (outside air); therefore,without the adhesion of dust in the peripheral atmosphere (outside air)onto the exit surface of the liquid crystal display element 2, no shadowis cast on the projection picture.

FIG. 6 is a cross-section view showing each element or portion of theliquid crystal display portion according to the fourth embodiment of thepresent invention.

The present embodiment differs from the third embodiment in an aspectthat a part including the connecting portion of the liquid crystaldisplay element 2 with the liquid crystal display element driving signalline 18 is constructed so as to be extended to an outside of the holdingmember 6 in which the cooling medium 5 is filled up with.

In the holding portion 62 of the holding member 6 is formed a hollowprojecting portion 62 b for attaching the liquid crystal display element2 thereon. In a part of the projecting portion 62 b is formed an opening62 c. A part of the liquid crystal display element 2 is fixed into theopening 62 c of the projecting portion 62 b in a condition of beingsealed liquid-tight, by means of a O-ring, adhesive, putty and so on.The connecting portion between the liquid crystal display element 2 andthe liquid crystal display element driving signal line 18 is located inthe opening within the projecting portion, thereby not contacting withthe cooling medium 5.

According to the present embodiment, in addition to the effect(s)mentioned in the third embodiment, there can be obtained another effectthat no consideration or concern is necessary for a corrosion-resistancecharacteristic against the cooling medium 5 of the connecting portionbetween the liquid crystal display element driving signal line 18 andthe liquid crystal display element 2, and electric leakage into thecooling medium 5 thereby. Next, an explanation will be given of thefifth to eleventh embodiments according to the present invention, byreferring to the attached drawings. Those are applied to thethree(3)-plate type liquid crystal projector. Of course, there may be acase where some of them can be applied to the structure of thesingle-plate type. However, in the drawings which will be explainedbelow, each of the structural elements which has the same function asthat of the embodiment mentioned in the above is attached with the samereference numeral.

FIG. 9 is a view showing the entire structure of an optical system ofthe three(3)-plate type liquid crystal projector according to thepresent embodiment.

The three(3)-plate type liquid crystal projector comprises liquidcrystal display portions 11R, 11G and 11B corresponding to therespective light components R, G and B. the light source 12 of such asthe metal halide lamp, the reflection mirror 13 for condensing the lightemitted from the light source 12 into a constant direction, the multiplelenses 14 and 15 constructed by assembling a large number of celllenses, the polarization conversion element (polarization conversionmeans) 17, a group of mirrors 34-39 constructing an optical separationsystem for dividing the polarized light into three (3) components,thereby separating the incident light into each of the components R, Gand B, condenser lenses 40R, 40G and 40B for condensing the incidentlights of the respective components, R, G and B upon the liquid crystaldisplay portions 11R, 11G and 11B, an optical composing element 41 forcomposing or synthesizing the light emitted from the liquid crystaldisplay portions 11R, 11G and 11B, and the projection lens 1 forprojecting the composed or synthesized image on the screen 16.

Here, the optical light source system is constructed with those elementsfrom the light source 12 up to the condenser lenses 40R, 40 G and 40B.Further, the optical projection system is constructed with the opticalelements, including the composing element 41, the projection lens 1 andso on.

Next, an explanation will be given of a fifth embodiment of the presentinvention, by referring to FIGS. 8 and 7.

FIG. 8 is a view of showing the construction in which the liquid crystaldisplay portions 11 are provided corresponding to each of the colorcomponents (R, G, B). However, in the figure, the heat radiator fin 19and the pressure adjusting chamber 25 are not shown therein.

In FIG. 8, the liquid crystal display portions 11R, 11G and 11B comprisethe liquid crystal display elements 2R, 2G and 2B, the incident sidepolarizing elements 3Ra, 3Ga and 3Ba, the exit side polarizing elements3Rb, 3Gb and 3Bb, the incident side polarizing element holding frame4Ra, 4Ga and 4Ba for holding and fixing the incident side polarizingelements 3Ra, 3Ga and 3Ba, and the holding members 6R, 6G and 6B.However, the references 5R, 5G and 5B indicate the cooling medium. Areference 41 indicates the optical composing element and 1 theprojection lens.

The liquid crystal display portions 11R, 11G and 11B are fixed onto thethree incident surfaces of an optical polyhedron, i.e., the opticalcomposing element 41. The optical composing element 41 is for composingor synthesizing the lights of respective color components passingthrough each of the liquid crystal display portions 11R, 11G and 11B.

The lights of the respective color components separated by the opticalseparation system which will be mentioned later are incident upon thecorresponding liquid crystal display portions 11R, 11G and 11B,respectively, thereby being dimmed for each pixel through the liquidcrystal display elements 2R, 2G and 2B. Each light dimmed, after beingcomposed or synthesized by the optical composing element 41, isprojected through the projection lens 1.

However, in the present embodiment, although the liquid crystal displayportions 11R, 11G and 11B are provided corresponding to the three (3)components R, G and B, other constructions are also possible, forinstance, the liquid crystal display portions 11 are corresponding totwo (2) components, such as Y and C, or G and R+B, or corresponding tocomponents equal to or more than four (4).

FIG. 7 is a cross-section view showing the detailed construction of theliquid crystal display parts in the fifth embodiment of the presentinvention. In the three-plate type, as shown in FIG. 8, the liquidcrystal display portions 11R, 11G and 11B are formed on the threeincident surfaces of the optical synthesizing element. However,basically, these liquid crystal display portions have the sameconstruction as one another, therefore, here will be explained thestructure corresponding only to one of the three components, R, G and B.Therefore, with the reference numerals attached, they are sometimes usedwithout distinguishing among R, G and B. Further, the example shown inFIG. 7 can be applied not only to that of the three-plate type, but alsois applicable to the single-plate type.

In FIG. 7, a reference numeral 41 indicates the optical composingelement of polyhedron shape, and 11 the liquid crystal display portion.In the present embodiment, the incident side polarizing element 3 a, theliquid crystal display element 2, the exit side polarizing element 3 b,and the optical composing element 41 are so disposed that they are inparallel to one another in the light penetrating or transmittingsurfaces thereof.

In the present embodiment, the holding member 6 adopts the one-piecestructure being formed in a concave shape. In this holding member, thereare provided the exit side opening 6 b as an opening of the concaveportion thereof, the incident side opening 6 a which is positioned at abottom of the concave portion, and a communication opening 6 c forcommunicating with the pressure adjusting chamber 25. The incident sideopening 6 a is inserted and sealed with the liquid crystal displayelement 2. In more detail, into the incident side opening 6 a isinserted the liquid crystal display element 2, and the elastic body 20is press-fitted into the aperture between them. Further, the exit sideopening 6 b is closely contacted and sealed with the opticalsynthesizing element 41. In more detail, the exit side opening 6 b iscovered with one of the incident surfaces of the optical composingelement 41, and is fixed to the optical composing element 41 through theO-ring 7. Both the incident side opening 6 a and the exit side opening 6b have sizes such that they will not interrupt the incident light andthe exiting light of the liquid crystal display element 2 therewith.

The holding member 6 is, as mentioned previously, made of a material ofgood thermal conductivity, such as, Fe, Cu, Al, Mg and so on, ormaterials containing them therein and being superior in thermalconductivity thereof, thereby carrying the role of heat radiation byitself. However, as the means for fixing the liquid crystal displayelement 2 and the optical composing element 41 onto the holding member6, an adhesive, putty or curable resin can be used in place of theelastic body 20 and/or the O-ring 7.

Upon the incident surface of the optical composing element 41 are fixedthe exit side polarizing element 3 b through the adhesive or a two-sidedadhesive tape, or the like. The exit incident side polarizing element 3a is positioned with a constant distance between the liquid crystaldisplay element 2, and is supported by the incident side polarizingelement holding frame 4 a. Here, the incident side polarizing elementholding frame 4 a has such a shape that it will not interrupt the lightincident upon the liquid crystal display element 2.

The pressure adjusting chamber 25 is communicated with an inside of theholding member 6, and is attached with the pressure adjusting bellows 9through the pressure adjusting bellows pressing plate 10. The spacewhich is surrounded by the liquid crystal element 2, the holding member6, the pressure adjusting chamber 25, the pressure adjusting bellows 9and the optical composing element 41 attached with the exit sidepolarizing element 3 b, is in a condition of being sealed liquid-tight,and is filled up with the cooling medium 5 therein. With such astructure, the liquid crystal element 2 and the exit side polarizingelement 3 b are held under the condition that they contact with thecooling medium 5.

In the cooling medium pressure adjusting chamber 25, the pressureadjusting bellows 9 is fixed by the pressure adjusting bellows pressingplate 10. The space which is surrounded by the liquid crystal displayelement 2 and the optical composing element 41, and the space which issurrounded by the cooling medium pressure adjusting chamber 25 and thepressure adjusting bellows 9, are communicated to each other, and thecooling medium 5 is in a condition of being movable therebetween. Thevolume change of the cooling medium 5 due to the change of temperatureis absorbed by the expansion and shrinkage or deformation of thepressure adjusting bellows 9. Thereby, the pressure in the holdingmember 6 is maintained constant.

A part of the heat generated in the liquid crystal display element 2 istransferred through the elastic body 20 to the holding member 6, and isdischarged outside the liquid crystal display portion 11. Most of therest of the heat generated is absorbed into the cooling medium 5, and ismoved following the convection current of the cooling medium 5. Then, itis transferred to the internal wall surface of the holding member 6 tobe discharged outside. In the same manner, most of the heat generated inthe exit side polarizing element 3 b is also absorbed into the coolingmedium 5 to be discharged outside.

In this way, the holding member 6 has the function of discharging theheat generated in the liquid crystal display portion 11 by itself.Therefore, it does not need a cooling mechanism, such as a heat pipe,and is simple in the construction thereof.

With provision of the heat radiator fin 19 on the outer wall of theholding member 6, it is possible to increase the efficiency of heatradiation. In a case where the heat radiation is performed with thenatural convection current of the air, it is preferable that the heatradiator fin 19 be so disposed that the heat radiating surfaces thereofare almost in parallel to the vertical direction, in particular. Withthe compulsive cooling of the holding member 6 through the cooling fanor the like, the efficiency of heat radiating can be increased, muchmore. In this case, it is preferable that the heat radiator fin 19 bedisposed so that the heat radiating surfaces thereof are almost inparallel to the direction of the air flow of the cooler fan.

A part of the heat generated in the incident side polarizing element 3 ais transferred to the periphery portion through contact thermalconduction, and a part of the rest of it is heat-exchanged between theperipheral atmosphere. By causing the air flow upon the surface of theincident side polarization element 3 a with use of the cooling fan, itmay be cooled, compulsively.

As the structural material (not shown in the figure) for holding andfixing the liquid crystal display portion 11, a material of good thermalconductivity, such as, Fe, Al and so on, or materials containing them,and being superior in thermal conductivity may be used, therebyaccelerating the heat radiation to the outside of the liquid crystaldisplay portion 11 through the contact thermal conduction.

In the present embodiment, since at least the incident side portion ofthe liquid crystal display element 2 faces to the outer portion of theholding member 6, the electrical connection between the liquid crystaldisplay element 2 and the liquid crystal display element driving signalline 18 is provided outside the holding member 6, thereby prohibitingthe electrical connection and the liquid crystal display element drivingsignal line 18 from contacting with the cooling medium 5. Therefore,there is no necessity for a measure of protecting from the encroachmentor corrosion by the cooling medium 5.

Further, the exit surface of the liquid crystal display element 2 is outof contact with the peripheral atmosphere (outside air), therefore, nodust in the peripheral atmosphere attaches upon the surface at the exitside of the liquid crystal display element 2, and no shadow thereof isprojected on the projected picture.

However, the exit side polarizing element 3 b need not necessarily beone piece as in the present embodiment, but can be constructed with aplurality of pieces thereof, and the effect of the present invention isstill effective, even in a case where only a part of the plural piecesare attached onto the liquid crystal display element 2.

In the construction above, as shown in FIG. 9, the light emitted fromthe light source 12 is condensed to the multiple lenses 14 and 15 by thereflection mirror 13. Here, the multiple lenses 14 and 15 have thefunction of entering the light over the total area of the display pixelregion of the liquid crystal display elements 2R, 2G and 2B, equally,thereby enabling the uniform brightness over the screen 16. The lightpassing through the multiple lenses 14 and 15, after being convertedinto the polarized light almost in parallel to the polarizationdirection of the incident side polarizing element 3 by the polarizationconverting element 17, is separated into the respective components, R, Gand B, through the optical separation system 34-39. The separatedcomponents, R, G and B, through the condenser lenses 40R, 40G and 40B,are incident upon the liquid crystal display elements 11R, 11G and 11B,respectively. Then, the lights of the respective components R, G and B,which are adjusted in the darkness for each pixel in the liquid crystaldisplay elements 11R, 11G and 11B, are projected through the projectionlens 1 upon the screen 16, after being composed or synthesized in theoptical composing element 41.

In the present embodiment, with use of the polarization convertingelement 17, an amount of light comes to be small, which is absorbed ineach incident side polarizing element 3 a. With this, an amount of heatgeneration in each incident side polarizing element 3 a is reduced,greatly, comparing to that of the case where no such polarizationconverting element 17 is used.

Further, by laying the cooling medium between the liquid crystal displayelement 2 and the exit side polarization element 3 b, which is near tothem in the refractive index thereof, the reflection can be reducedbetween them on the optical path, thereby realizing the high brightnesswhile protecting from the reduction in brightness, as well as achievingthe suppression in the contrast of the projected picture. Further, theliquid crystal display element 2 and the exit side polarizing element 3b are cooled by the cooling medium 5; therefore, the increase in theirtemperature can be suppressed. Moreover, without necessity of specialoptical elements, the simplification of the liquid crystal displayportion 11 can be obtained.

Furthermore, according to the present embodiment, since the light isdimmed or adjusted on display for each one of the pixels on the screen16, by use of the plurality of liquid crystal display elements 2, thequality of the displayed picture can be improved.

FIG. 10 is a cross-section view showing the construction of the liquidcrystal display portions at the periphery of the optical composingelement in the sixth embodiment of the present invention.

The present embodiment differs from the fifth embodiment in aspects thatthe sealed spaces of the cooling medium 5 for the respective liquidcrystal-display portions 11R, 11G and 11B are connected to one another,only one holding member 6 is used for the respective liquid crystaldisplay elements 2R, 2G and 2B, and the exit side polarizing elements3Rb, 3Gb, 3Bb are provided at the exit surfaces of the correspondingliquid crystal display elements 2R, 2G and 2B.

The holding member 6 is formed in box-like shape as a whole, in whichare provided incident side openings 6Ra, 6Ga, 6Ba for inserting therespective liquid crystal display elements 2R, 2G and 2B therein, and anexit side opening 6 b for inserting the optical composing element 41therein. Within the space which is surrounded by the optical composingelement 41, the holding member 6 and the plurality of the liquid crystaldisplay elements 2R, 2G and 2B, the cooling medium 5 is filled.

Because of this construction, the holding member 6 holds the exit sidepolarizing elements 3Rb, 3Gb, 3Bb through the respective liquid crystaldisplay elements 2R, 2G and 2B, so as to make at least the exit sidepolarizing elements 3Rb, 3Gb, 3Bb contact with the cooling medium 5.Accordingly, in the present embodiment, the exit side polarizingelements 3Rb, 3Gb, 3Bb are in contact with the cooling medium 5 to becooled, and the respective liquid crystal display elements 2R, 2G and 2Bare also cooled through the exit side polarizing elements 3Rb, 3Gb, 3Bb.

In the case of the present embodiment, when the heat generation isincreased in a part of the liquid crystal display elements 2 and/or theexit side polarizing elements 3, depending on the kind of the displayedpicture, since this heat is dispersed into the cooling space as a whole,which is constructed with the holding member 6, by means of theconvection current of the cooling medium 5, the efficiency of the heatradiation is improved.

Further, with this construction, only one of the pressure adjustingmechanisms (omitted in the figure) is enough to be provided forabsorbing the volume change of the cooling medium due to the change intemperature thereof, therefore, the apparatus itself can be simplified.

Further, in the present embodiment, the exit side polarizing elements3Rb, 3Gb, 3Bb are fixed on the exit surfaces of the liquid crystaldisplay elements 2R, 2G and 2B, respectively, thereby enabling astructure, in which the penetrating or transmitting axis of thepolarized light in the exit side polarizing element 3 is positioned andfixed with high accuracy relating to the liquid crystal display element2. Because of this, the permeability or transmittance when displayingwhite in total, and a shielding ratio when displaying black in total,are improved, thereby enabling a display of high contrast.

However, in the present embodiment, the exit side polarizing element 3can be fixed onto the optical composing element.

FIG. 11 is a cross-section view showing the construction of the liquidcrystal display portion 11 in the seventh embodiment of the presentinvention. In FIG. 11, the reference numeral 41 indicates the opticalcomposing element, and 2 the liquid crystal display element. In thepresent embodiment, the incident side polarizing element 3 a, the liquidcrystal display element 2, the exit side polarizing element 3 b, and theoptical composing element 41 are so disposed that they are in parallelto one another, in particular, with the light penetrating ortransmitting surfaces thereof.

In the present embodiment, the holding member 6 adopts the one-piecestructure which has a concave shape. In this holding member 6 areprovided-the exit side opening 6 b as an opening of the concave portionthereof, the incident side opening 6 a which is positioned at a bottomof the concave portion, an opening 6 d for the pressure adjustingbellows 9, and an opening 6 e for extension of the signal line. Theincident side opening 6 a is inserted and sealed with the incident sidepolarizing element 3 a. Further, the exit side opening 6 b is closelycontacted and sealed with the optical composing element 41. In moredetail, the exit side opening 6 b is covered with one of the lightincident surfaces of the optical composing element 41, and is fixed tothe optical composing element 41 through the O-ring 7. Both the incidentside opening 6 a and the exit side opening 6 b are have sizes such thatthe incident light and the emitting light of the liquid crystal displayelement 2 will not be interrupted therewith. Further, in the opening 6 eis inserted the signal line 18 therethrough, and is sealed by a sealingmember 22.

The liquid crystal display element driving signal line 18 is extendedfrom the signal line extension opening 6 e to an outside of the holdingmember 6. As the sealing member 22 for sealing the holding member 6,filling-up of the adhesive or the curable resin, or alternativelypressure-fitting of the elastic body and so on, can be applied. With thesealing portion being formed in this way, it is possible to extend theliquid crystal display element driving signal line 18 to the outside ofthe container.

The cooling medium 5 is filled up within the space being surrounded bythe incident side polarization element 3 a, the pressure adjustingbellows 9 and the optical composing element 41 on which the exit sidepolarizing element 3 b is fixed. The present embodiment differs from thefifth embodiment in an aspect that a light passage region defined fromthe exit surface of the incident side polarizing element 3 a up to theincident surface of the exit side polarizing element 3 b is filled upwith the cooling medium 5, with positioning the liquid crystal displayelement 2 between them. However, the exit side polarizing element 3 b,as is explained in FIG. 10, may be fixed onto the exit surface of theliquid crystal display element 2.

In FIG. 11, the reference numeral 24 indicates the liquid crystaldisplay element holding frame for supporting the liquid crystal displayelement 2. The liquid crystal display element 2 comes to be disposedwithin the cooling medium 5 through the liquid crystal display elementholding frame 24. Here, the region within which the cooling medium 5 isfilled up is communicated with the incident surface side and the exitsurface side of the liquid crystal display element 2. Thereby, it is soconstructed that the cooling medium 5 can move between both regionsfreely and contacts with the outside of the liquid crystal displayelement 2 as a whole, to be cooled down.

According to the present embodiment, since both the incident surface andthe exit surface of the liquid crystal display element 2 contact withthe cooling medium 5 directly to be cooled therewith, the increase intemperature of the liquid crystal display element 2 can be reduced muchmore. Also the heat generation in the incident side polarizing element 3a can be cooled by the cooling medium 5.

Further, since both surfaces of the liquid crystal display element 2 areout of contact with the peripheral atmosphere (outer air), no dust inthe peripheral atmosphere can be attached onto the surface of the liquidcrystal display element 2, and no shadow is projected upon the projectedpicture.

FIG. 12 is a cross-section view showing the construction of the liquidcrystal portion at the periphery of the optical composing element in theeighth embodiment of the present invention.

The present embodiment is characterized in that the holding member 6 inthe seventh embodiment shown in the previous-mentioned FIG. 11 is. incommon with the three components R, G and B, as shown in FIG. 10.Namely, the holding member 6 in the present embodiment is shaped as awhole like a box, in which are provided the incident side openings 6Ra,6Ga and 6Ba for inserting the incident side polarizing elements 3Ra, 3Gaand 3Ba corresponding to the respective liquid crystal display elements2R, 2G and 2B therein, and the exit side opening 6 b for inserting theoptical composing element 41 therein. Within the space surrounded by theoptical composing element 41, the holding member 6, and the plurality ofincident side polarizing elements 3Ra, 3Ga and 3Ba, the cooling medium 5is filled.

With such a construction, the holding member 6 holds the incident sidepolarizing elements 3Ra, 3Ga and 3Ba, the liquid crystal displayelements 2R, 2G and 2B, and the exit side polarizing elements 3Rb, 3Gband 3Bb in such manner that they contact with the cooling medium 5 to becooled. The liquid crystal display elements 2R, 2G and 2B, and the exitside polarizing elements 3Rb, 3Gb and 3Bb, though being omitted in FIG.12, are supported by the liquid crystal display element holding member24 shown in FIG. 11.

With the construction, since the cooling medium 5 can move freelybetween the respective liquid crystal display elements 2R, 2G and 2B,the cooling capacity or efficiency is increased. Further, it is enoughto provide only one pressure adjusting mechanism (9, 10) therein.

However, it can be so constructed that the exit side polarizing elements3Rb, 3Gb and 3Bb are fixed onto the optical composing element 41.

FIG. 13 is a cross-section view showing the construction of the liquidcrystal portion at the periphery of the optical composing element in theninth embodiment of the present invention.

The present embodiment differs from the eighth embodiment in an aspectthat the optical composing element 41 is positioned within the holdingmember 6 and the exit side opening of the holding member 6 is sealedwith the first projection lens 1 constructing the projection means.other aspects of the construction are the same as those of the eighthembodiment. In the construction of the present embodiment, the incidentsurface and the exit surface of the optical composing element 41 contactwith the cooling medium 5 directly, and also the space between theoptical composing element 41 and the first projection lens 1 is filledup with the cooling medium 5.

Next, an explanation will be given of the tenth embodiment shown in FIG.14. The present embodiment has basically the same construction as thatof the fifth embodiment shown in FIG. 7. The difference lies in th atthe exit side polarizing element 3 b is fixed independently, and thereis no separate pressure adjusting chamber.

As shown in FIG. 14, in the present embodiment, the incident sidepolarizing element 3 a, the liquid crystal display element 2, the exitside polarizing element 3 b and the optical composing element 41 are sodisposed that this light penetrating or transmitting surfaces are inparallel to one another.

In the present embodiment, the holding member 6 adopts the one-piecestructure which has a concave shape. In this holding member 6 areprovided the exit side opening 6 b as an opening of the concave portionthereof, the incident side opening 6 a which is positioned at a bottomof the concave portion, and an opening 6 d for installing the pressureadjusting bellows 9 therein. The incident side opening 6 a is insertedand sealed with the liquid crystal display element 2. In more detail,into the incident side opening 6 a is inserted the liquid crystaldisplay element 2, and the elastic body 20 is press-fitted into theaperture between them. Further, the exit side opening 6 b is closelycontacted and sealed with the optical composing element 41. In moredetail, the exit side opening 6 b is covered with one of the lightincident surfaces of the optical composing element 41, and is fixed tothe optical composing element 41 through the O-ring 7. Both the incidentside opening 6 a and the exit side opening 6 b have sizes such that theywill not interrupt the incident light and the exiting light of theliquid crystal display element 2.

Further, in FIG. 14, the reference numeral 4 b indicates the exit sidepolarizing element holding frame. The exit side polarizing element 3 bis positioned at a constant distance from the liquid crystal displayelement 2 and the optical composing element 41, and is fixed onto theholding member 6 by the exit side polarizing element holding frame 4 b.Here, the exit side polarizing element holding frame 4 b has such ashape that the cooling medium 5 can move between the incident surfaceand the exit surface of the exit side polarizing element 3 b. As aresult of this, both the incident surface and the exit surface of theexit side polarizing element 3 b are cooled by the cooling medium 5,thereby improving the cooling capacity or efficiency with respect to theexit side polarizing element 3 b.

Further, as shown in FIG. 14, the present embodiment is so constructedthat the pressure adjusting mechanism of the cooling medium 5 is unifiedwith the holding member 6 as a unit. Namely, a bellows insertion opening6 d is provided in the holding member 6, in place of the communicatingopening of the pressure adjusting chamber, and there is provided thepressure adjusting bellows 9 which is fixed by the pressure adjustingbellows pressing plate 10. With this construction, there is no necessityof the pressure adjusting chamber, and the number of the parts of theliquid crystal display portion 11, as well as the number of themanufacturing processes thereof, can be cut back.

FIG. 15 is a cross-section view showing the construction of the liquidcrystal portion in the eleventh embodiment of the present invention.

In the present embodiment, a step-like portion 60 is provided in a partof the bottom surface side of the holding member 6 of the one-piecestructure, and on a wall surface 60 a of the step-like portion 60 isfixed the liquid crystal display element 2. In the wall surface 60 a isprovided an opening so as to extend the liquid crystal display elementdriving signal line 18 therethrough. Apart of the liquid crystal displayelement 2 is fixed onto the wall surface 60 a of the step-like portion,by means of an O-ring, adhesive, putty and so on, in the condition ofbeing sealed liquid-tight. The connection between the liquid crystaldisplay element 2 and the liquid crystal display element driving signalline 18 is so arranged that the corridor will not contact with thecooling medium 5.

Further, at the incident side of the holding member 6 is provided theincident side opening 6 a, in a vicinity of the wall surface 60 a of theabove-mentioned step-like portion 60. Further, the holding member is ina concave shape as a whole, and an opening of the concave portion formsthe exit side opening 6 b. In the incident side opening 6 a is insertedthe incident side polarizing element 3 a, which seals the cooling medium5 liquid-tightly. Further, in the exit side opening 6 b, the opticalcomposing element 41 is inserted and fixed through the adhesive 21. Thisadhesive 21 also has the function of sealing the interior space of theholding member 6.

According to the present embodiment, in addition to the effectsmentioned in the previously-mentioned seventh embodiment, another effectcan be obtained that no consideration or measure is necessary for thecorrosion resistance at the connection between the liquid crystaldisplay element driving signal line 18 and the liquid crystal displayelement 2 against the cooling medium 5, electric leakage to the coolingmedium 5, and so on.

Further, in the present embodiment, the optical composing element 41 isso constructed that it is fixed onto the wall surface 60 a of thestep-like portion of the holding member 6, therefore, it is easy toposition the liquid crystal display element 2 and/or the other opticalelements which are assembled on the holding member 6 relating to theoptical composing element 41. Because of this, work, such as fitting theoptical axis of the optical composing element 41 to that of the otheroptical elements, and so on, comes to be easy to perform.

As is fully mentioned in the above, according to the various embodimentsof the present invention, the exit side polarizing element 3 b contactwith the cooling medium 5 to be cooled, whereby the heat generation iscooled down effectively. Further, with liquid crystal display portion 2is cooled by the cooling medium 5 directly or indirectly through theabove-mentioned exit side polarizing element 3 b. Though it is mosteffective when the liquid crystal display element(s) is cooled by thecooling medium 5 directly, however, it also can be cooled effectivelysince the thermal conduction occurs all over the surface of the exitside polarizing element 3 b as a whole, in a direction of the thicknessthereof, even when it is cooled through the exit side polarizing element3 b.

As is mentioned in the above, according to the present invention, it ispossible to achieve high brightness in the projection picture, as wellas suppression of the increase in temperature of the liquid crystaldisplay element(s) and the polarizing element(s) at the same time.Further, it is also possible to suppress the decrease in contrast.Furthermore, there can be provided a liquid crystal display apparatuswhich can be realized with small size and simplified construction.

The present invention, without deviating from the spirit or principalfeatures thereof, can be applied to embodiments other than thosementioned in the above. Accordingly, the embodiments mentioned above areonly one examples of the present invention, and they should not beinterpreted restrictively. The scope of the present invention isindicated by the pending claims, and further, all variations andmodifications which belong to the invention and equivalents thereof arealso within the scope of the present invention.

What is claimed is:
 1. A liquid crystal display apparatus, comprising:an optical source system for emitting projection light; a liquid crystaldisplay portion, arranged to receive the projection light from saidoptical source system and to generate a projection picture dependingupon a driver signal; an optical projection system, including a firstoptical element which receives a light emitted from said liquid crystaldisplay portion, arranged to project the light emitted from said liquidcrystal display portion towards a projection object; wherein said liquidcrystal display portion comprises: a liquid crystal display element forgenerating the picture; an incident side polarizing element positionedat an incident side of said liquid crystal display element; an exit sidepolarizing element positioned at an exit side of said liquid crystaldisplay element; a holding member arranged to hold at least the liquidcrystal display element, the exit side polarizing element and said firstoptical element; and a cooling medium: wherein either of said incidentside polarizing element or said liquid crystal display element, saidfirst optical element and said holding member define a space betweensaid liquid crystal display element and said first optical element, andsaid cooling medium is filled up within said space so that said coolingmedium contacts an entire light transmitting surface of at least one ofsaid liquid crystal display element and said exit side polarizingelement.
 2. A liquid crystal display apparatus, as described in claim 1,wherein said exit side polarizing element is positioned at an incidentsurface of said first optical element.
 3. A liquid crystal displayapparatus, as described in claim 1, wherein said exit side polarizingelement is positioned at an exit surface of said liquid crystal displayelement.
 4. A liquid crystal display apparatus, as described in claim 1,wherein said exit side polarizing element is located between said liquidcrystal display element and said first optical element, and ispositioned under condition of being apart from both of them.
 5. A liquidcrystal display apparatus, as described in claim 1, wherein said holdingmember has openings at the incident side and the exit side,respectively, and further, at said incident side opening is installedany one of said incident side polarizing element and said liquid crystaldisplay element, and at said exit side opening is installed said firstoptical element.
 6. A liquid crystal display apparatus, as described inclaim 5, wherein at the incident side opening of said holding member isinstalled said incident side polarizing element, and said liquid crystaldisplay element is held by said holding member under condition that thecooling medium lies on both surfaces at the incident side and the exitside thereof.
 7. A liquid crystal display apparatus, as described inclaim 5, wherein at the incident side opening of said holding member isinstalled said liquid crystal display element, and said liquid crystaldisplay element is held by said holding member under condition that thecooling medium lies on a surface of the incident side thereof.
 8. Aliquid crystal display apparatus, as described in claim 1, wherein saidliquid crystal display element is held by said holding member undercondition that at least said exit side polarizing element contacts withsaid cooling medium.
 9. A liquid crystal display apparatus, as describedin claim 2, wherein said liquid crystal display element is held by saidholding member under condition that at least said exit side polarizingelement contacts with said cooling medium.
 10. A liquid crystal displayapparatus, as described in claim 3, wherein said liquid crystal displayelement is held by said holding member under condition that at leastsaid exit side polarizing element contacts with said cooling medium. 11.A liquid crystal display apparatus, as described in claim 4, whereinsaid liquid crystal display element is held by said holding member undercondition that at least said exit side polarizing element contacts withsaid cooling medium.
 12. A liquid crystal display apparatus, asdescribed in claim 5, wherein said liquid crystal display element isheld by said holding member under condition that at least said exit sidepolarizing element contacts with said cooling medium.
 13. A liquidcrystal display apparatus, as described in claim 6, wherein said liquidcrystal display element is held by said holding member under conditionthat at least said exit side polarizing element contacts with saidcooling medium.
 14. A liquid crystal display apparatus, as described inclaim 7, wherein said liquid crystal display element is held by saidholding member under condition that at least said exit side polarizingelement contacts with said cooling medium.
 15. A liquid crystal displayapparatus, as described in claim 1, wherein said cooling medium has arefractive index near to that of said exit side polarizing element. 16.A liquid crystal display apparatus, as described in claim 2, whereinsaid cooling medium has a refractive index near to that of said exitside polarizing element.
 17. A liquid crystal display apparatus, asdescribed in claim 3, wherein said cooling medium has a refractive indexnear to that of said exit side polarizing element.
 18. A liquid crystaldisplay apparatus, as described in claim 4, wherein said cooling mediumhas a refractive index near to that of said exit side polarizingelement.
 19. A liquid crystal display apparatus, as described in claim5, wherein said cooling medium has a refractive index near to that ofsaid exit side polarizing element.
 20. A liquid crystal displayapparatus, as described in claim 6, wherein said cooling medium has arefractive index near to that of said exit side polarizing element. 21.A liquid crystal display apparatus, as described in claim 7, whereinsaid cooling medium has a refractive index near to that of said exitside polarizing element.
 22. A liquid crystal display apparatus, asdescribed in claim 1, wherein a refractive index of said cooling mediumlies within a range from 1.2 to 1.7.
 23. A liquid crystal displayapparatus, as described in claim 2, wherein a refractive index of saidcooling medium lies within a range from 1.2 to 1.7.
 24. A liquid crystaldisplay apparatus, as described in claim 3, wherein a refractive indexof said cooling medium lies within a range from 1.2 to 1.7.
 25. A liquidcrystal display apparatus, as described in claim 4, wherein a refractiveindex of said cooling medium lies within a range from 1.2 to 1.7.
 26. Aliquid crystal display apparatus, as described in claim 5, wherein arefractive index of said cooling medium lies within a range from 1.2 to1.7.
 27. A liquid crystal display apparatus, as described in claim 6,wherein a refractive index of said cooling medium lies within a rangefrom 1.2 to 1.7.
 28. A liquid crystal display apparatus, as described inclaim 7, wherein a refractive index of said cooling medium lies within arange from 1.2 to 1.7.
 29. A liquid crystal display apparatus, asdescribed in claim 1, wherein said holding member is made of metal andprovided with a heat radiation fin.
 30. A liquid crystal displayapparatus, as described in claim 2, wherein said holding member is madeof metal and provided with a heat radiation fin.
 31. A liquid crystaldisplay apparatus, as described in claim 3, wherein said holding memberis made of metal and provided with a heat radiation fin.
 32. A liquidcrystal display apparatus, as described in claim 4, wherein said holdingmember is made of metal and provided with a heat radiation fin.
 33. Aliquid crystal display apparatus, as described in claim 5, wherein saidholding member is made of metal and provided with a heat radiation fin.34. A liquid crystal display apparatus, as described in claim 6, whereinsaid holding member is made of metal and provided with a heat radiationfin.
 35. A liquid crystal display apparatus, as described in claim 7,wherein said holding member is made of metal and provided with a heatradiation fin.
 36. A liquid crystal display apparatus, as described inclaim 1, wherein said holding member is made of metal and provided witha pressure adjusting mechanism.
 37. A liquid crystal display apparatus,as described in claim 2, wherein said holding member is made of metaland provided with a pressure adjusting mechanism.
 38. A liquid crystaldisplay apparatus, as described in claim 3, wherein said holding memberis made of metal and provided with a pressure adjusting mechanism.
 39. Aliquid crystal display apparatus, as described in claim 4, wherein saidholding member is made of metal and provided with a pressure adjustingmechanism.
 40. A liquid crystal display apparatus, as described in claim5, wherein said holding member is made of metal and provided with apressure adjusting mechanism.
 41. A liquid crystal display apparatus, asdescribed in claim 6, wherein said holding member is made of metal andprovided with a pressure adjusting mechanism.
 42. A liquid crystaldisplay apparatus, as described in claim 7, wherein said holding memberis made of metal and provided with a pressure adjustment mechanism. 43.A liquid crystal display apparatus, as described in claim 1, whereinsaid optical source system comprises a light source and an element forconverting the polarization of a light projected from the light source,so that the incident light upon said incident side polarizing elementcomes to be a polarized light including a polarization component that isparallel to a polarization direction of said incident side polarizingelement.
 44. A liquid crystal display apparatus, as described in claim2, wherein said optical source system comprises a light source and anelement for converting the polarization of a light projected from thelight source, so that the incident light upon said incident sidepolarizing element comes to be a polarized light including apolarization component that is parallel to a polarization direction ofsaid incident side polarizing element.
 45. A liquid crystal displayapparatus, as described in claim 3, wherein said optical source systemcomprises a light source, and an element for converting the polarizationof a light projected from the light source, so that the incident lightupon said incident side polarizing element comes to be a polarized lightincluding a polarization component that is parallel to a polarizationdirection of said incident side polarizing element.
 46. A liquid crystaldisplay apparatus, as described in claim 4, wherein said optical sourcesystem comprises a light source, and an element for converting thepolarization of a light projected from the light source, so that theincident light upon said incident side polarizing element comes to be apolarized light including a polarization component that is parallel to apolarization direction of said incident side polarizing element.
 47. Aliquid crystal display apparatus, as described in claim 5, wherein saidoptical source system comprises a light source, and an element forconverting the polarization of a light projected from the light source,so that the incident light upon said incident side polarizing elementcomes to be a polarized light including a polarization component that isparallel to a polarization direction of said incident side polarizingelement.
 48. A liquid crystal display apparatus, as described in claim6, wherein said optical source system comprises a light source, and anelement for converting the polarization of a light projected from thelight source, so that the incident light upon said incident sidepolarizing element comes to be a polarized light including apolarization component that is parallel to a polarization direction ofsaid incident side polarizing element.
 49. A liquid crystal displayapparatus, as described in claim 7, wherein said optical source systemcomprises a light source, and an element for converting the polarizationof a light projected from the light source, so that the incident lightupon said incident side polarizing element comes to be a polarized lightincluding a polarization component that is parallel to a polarizationdirection of said incident side polarizing element.
 50. A liquid crystaldisplay apparatus, comprising: an optical source system for emittingprojection light; a plurality of liquid crystal display portions,arranged to receive the projection light from said optical source systemand to generate a projection picture depending upon a driver signal; aprojection optical system arranged to compose and project the lightemitted from said plurality of liquid crystal display portions towards aprojection object, wherein: said optical source system has a lightsource and an optical separation system for dividing and emitting thelight emitted from the light source towards said plurality of liquidcrystal display portions; and said projection optical system has a firstoptical element arranged to compose lights emitted from said pluralityof liquid crystal display portions and a second optical element forprojecting the light composed, and further, each of said liquid crystaldisplay portions comprises: a liquid crystal display element forgenerating the picture; an incident side polarizing element positionedat an incident side of said liquid crystal display element; an exit sidepolarizing element positioned at an exit side of said liquid crystaldisplay element; a holding member arranged to hold at least the liquidcrystal display element, the exit side polarizing element and said firstoptical element in each of said liquid crystal display portions; and acooling medium: wherein either said incident side polarizing element orsaid liquid crystal display element, said first optical element and saidholding member define a space between said liquid crystal displayelement and said first optical element, and said cooling medium isfilled up within said space so that said cooling medium contacts anentire light transmitting surface of at least one of said liquid crystaldisplay element and said exit side polarizing element.
 51. A liquidcrystal display apparatus, as described in claim 50, wherein saidholding member is provided for each of said liquid crystal displayportions, and the space within which said cooling medium is filled up isdefined for each of said liquid crystal display portions.
 52. A liquidcrystal display apparatus, as described in claim 50, wherein saidholding member is provided in common for said liquid crystal displayportions, and the space within which said cooling medium is filled up isdefined as one space as a whole for said liquid crystal displayportions.
 53. A liquid crystal display apparatus, comprising: an opticalsource system for emitting projection light; a plurality of liquidcrystal display portions, arranged to receive the projection light fromsaid optical source system and to generate a projection picturedepending upon a driver signal; a projection optical system arranged tocompose and project the light emitted from said plurality of liquidcrystal display portions towards a projection object, wherein: saidoptical source system has a light source and a separation optical systemarranged to divide and exit a light emitted from the light source towardsaid plurality of liquid crystal display portions; and said projectionoptical system has a first optical element arranged to compose lightsemitted from said plurality of liquid crystal display portions and asecond optical element for projecting the light composed, and further,each of said liquid crystal display portions comprises: a liquid crystaldisplay element for generating the picture; an incident side polarizingelement positioned at an incident side of said liquid crystal displayelement; an exit side polarizing element positioned at an exit side ofsaid liquid crystal display element; a holding member arranged to holdat least the liquid crystal display element, the exit side polarizingelement and said second optical element; and a cooling medium: whereinsaid holding member is provided in common for said liquid crystaldisplay portions as well as in each of said liquid crystal displayportions; either of said incident side polarizing element or said liquidcrystal display element, said second optical element and said holdingmember define a space between said liquid crystal display element andsaid second optical element within which said cooling medium is filled;and the space is constructed as one space as a whole for the liquidcrystal display portions, such that said cooling medium contacts anentire light transmitting surface of at least one of said liquid crystaldisplay element and said exit side polarizing element.
 54. A liquidcrystal display apparatus, as described in claim 53, wherein said firstoptical element is received within said space.
 55. An optical device,including a liquid crystal display element within an optical path,comprising: an incident side polarizing element positioned at anincident side of said liquid crystal display element; an exit sidepolarizing element positioned at an exit side of said liquid crystaldisplay element; fixing means for fixing said incident side polarizingelement, said liquid crystal display element and said exit sidepolarizing element; a cooling medium; and holding means for holding saidcooling medium in contact with said exit side polarizing element.
 56. Anoptical device, as described in claim 55, wherein said holding meansholds said cooling medium in contact with said liquid crystal displayelement and said exit side polarizing element.
 57. An optical device, asdescribed in claim 55, wherein said holding means holds said coolingmedium in contact with said incident side polarization element, saidliquid crystal display element and said exit side polarizing element.58. An optical device, as described in claim 55, wherein an opticalelement, upon which is incident the light emitted from said exit sidepolarizing element, is provided at a stage after said exit sidepolarizing element, and said fixing means fixes said incident sidepolarizing element, said liquid crystal display element and said exitside polarizing element.
 59. An optical device, as described in claim55, further comprising first and second optical elements, upon which isincident the light emitted from said exit side polarizing element,provided at a stage after said exit side polarizing element, whereinsaid fixing means fixes said incident side polarizing element, saidliquid crystal display element and said exit side polarizing elementwith said second optical element, and fixes said first optical elementwithin said cooling medium.
 60. An optical device, as described in claim56, further comprising first and second optical elements, upon which isincident the light emitted from said exit side polarizing element,provided at a stage after said exit side polarizing element, whereinsaid fixing means fixes said incident side polarizing element, saidliquid crystal display element and said exit side polarizing elementwith said second optical element, and fixes said first optical elementwithin said cooling medium.
 61. An optical device, as described in claim57, further comprising first and second optical elements, upon which isincident the light emitted from said exit side polarizing element,provided at a stage after said exit side polarizing element, whereinsaid fixing means fixes said incident side polarizing element, saidliquid crystal display element and said exit side polarizing elementwith said second optical element, and fixes said first optical elementwithin said cooling medium.